The fighting style I had proposed above included several elements. 1) Instead of using an attack action of yours to direct the beast to attack, you can use a bonus action, and 2) If an opponent you are adjacent to strikes your companion, you can re-direct that attack to yourself instead, and if it hits, you have resistance to the damage from that attack. I'd say that covers a fair bit of ground.
Those also cover far more than any other Fighting Style. It sounds closer to half of a feat.
Also, if the Ranger is fine, why would they release this, since it is clearly only useful for the Beastmaster Ranger and no one else?
Then we get into the issue of choosing the fighting style before you actually get the Beast, meaning that you are essentially losing half of your second level to your third level choice. Unless we add in that the Beastmaster can choose a second style later on, which rewrites the class, which we are avoiding.
In terms of spells, they can be longer duration, and they can be low level. Resurrecting a beast easily seems pretty helpful, and shouldn't be needed many times per day.
I think those two additions would be enough. I've seen the beastmaster in play since it was published, and just those two tweaks would be more than enough in my experience to fix the issues with it.
Longer duration and lower level doesn't fully change the fact that rangers only get a VERY limited pool of spells. I mean, between levels 3 and 5 we get 3 and then 4 spells known. Adding a single spell that a Beastmaster will feel required to take will mean they are losing out on a 1/3 of their spell choices otherwise.
And, to make them both usefully powerful and not stolen by either Druids or Bards dipping, they need to be specific to Rangers and Ranger Animal Companions, which would again be a very strange choice for the company to make if the class does not need any assistance.
And if it needs assistance, why abandon the rewrite? A stealth rewrite is still a rewrite after all.
Right, she treated Trinket like a friend to be protected above all, rather than an expendable resource. Travis probably would have played a better Beastmaster Ranger on that count. This was the big misstep on the designers part, making a subclass focused on an expendable resource without thinking through people getting attached to their pet. This doesn't mean the subclass doesn't work as intended, but there was a mismatch between design intentions and the playstyle desired by many players. And, even not using the tools as intended, Laura still continued to contribute and have fun, the main metrics the designers are going for.
So, yet again, the subclass does not do what people would want it to do. But, she had fun playing the class and essentially ignoring her subclass so the subclass is fine?
And if they expected players to play with a conveyor belt of disposable bodies... then I'd say they're holding onto a style of DnD that hasn't been mainstream in over 20 years. That is a massive disconnect with the intended audience, but now more people are more comfortable ignoring their abilities so it is fine?
Honestly, your logic (if it gets taken and applied to all new content) brings into questions why we even have rules. If we don't need strong rules and well-balanced classes to have fun, then why do we bother having them? Because it provides a good support structure. Just because some people are having fun without those supports does not mean we shouldn't work to make sure those supports are included.
Millions of new players joined, bring millions of new approaches to playing the game. In addition, D&D Beyond took off int he meantime, and WotC now has solid numerical evidence of what people are doing, not just saying.
Let us not overstate things here. Millions of new people did not add "millions of new approaches to playing the game". We've had millions of players before over the lifetime of Dungeons and Dragons, and we still have only a handful of game playing approaches. I think the biggest number I've ever seen is like "13 player types" or something like that.
People have not revolutionized roleplaying games that much, that isn't how entertainment works.